A known electric telescopic apparatus for a vehicle seat, described in WO03/074318, includes a telescopic component having three telescopic elements (32, 33, 34), which adjust the electric telescopic apparatus to be telescopic using an electric spindle drive, which is capable of adjusting a length of a leg rest (3). According to the known apparatus, an automatic telescopic type drive is positioned in the center of the telescopic element (33) and includes an electric motor (35) permanently connected to the telescopic element (33). The top telescopic element (32) is driven by a first spindle drive (36) and the bottom telescopic element (34) is driven by a second spindle drive (37). When the electric motor (35) is activated to rotate in one direction, the top telescopic element (32) and the bottom telescopic element (34) move away from the center of the telescopic element (33). When the electric motor (35) is activated to rotate in the opposite direction, the top telescopic element (32) and the bottom telescopic element (34) are moved towards the center of the telescopic element (33). A first spindle nut (41) of the first spindle drive (36) is geared with a second spindle nut (42) of the second spindle drive (37) so as to rotate in the opposite directions from another. Thus, the electric motor (35) drives the first spindle drive (36) in the opposite direction from the second spindle drive (37) by driving the first spindle nut (41) of the first spindle drive (37).
With the construction of the electric telescopic apparatus for the vehicle seat described in WO03/074318, a support structure for rotatably supporting the first and second spindle drives (36, 37) is required, and a support structure for supporting the first and second spindle nuts (41, 42) which drive the first and second spindle drives (36, 37) by drive force of the electric motor (35) is also required. Because those support structures are thick in height, there is a drawback that a thickness of the electric telescopic apparatus per se cannot be reduced even if a motor is downsized. Further, because the first and second spindle drives (36, 37) are bar shaped, space for accommodating the bars are also required.
In addition, because the first spindle drive (36) has a cantilever structure where one end of the first spindle drive (36) is fixed to a frame and the other end is unattached, the strength is insufficient. Although countermeasures for reinforcement such as providing a construction that supports the first spindle drive at both ends may be devised in order to overcome this problem, this might bring other drawbacks that weight of the apparatus is increased leading to further structure complications.
A need thus exists for an electric telescopic apparatus for a vehicle seat, which has higher strength capabilities with a simple and thin construction.